1. Field of the Invention
This invention relates to guardrails, namely highway guardrails, and more particularly apparatus for making guardrails readily noticeable to drivers of motor vehicles on the highways and roadways having guardrails bordering the sides and medians between lanes of traffic on highways and roadways.
2. Description of the Prior Art
Guardrails bordering highways and roadways are well known in the United States and throughout the world. Highways are usually bordered with continuous, horizontal metal guardrails, having guardrail beams attached to regularly spaced vertical posts spaced at equal distances along the highways and roadways, and anchored to the ground. (Highways and roadways will hereinafter be defined as “highways.”) The continuous guardrail beams are generally attached to the vertically-anchored posts for holding one or more horizontal guardrail beams between the vertical posts.
The horizontal guardrail beam is generally composed of a continuous horizontal rail or beam which may have a double-wave shape, generally referred to as a W-beam made from standard heavy gauge metal. Each guardrail beam usually has at least two folds to provide a typical W-beam cross section. A series of post bolt holes and splice bolt slots are included in the guardrail beams so that they can be used interchangeably with existing guardrail systems. W-beam guardrails very often comply with the American Association of State Highway Transportation Official (AASHTO) Designation M180-89. Designation 180-89 Class Type A specifies that the overall length of the W-beam guardrail is respectively 4.318 meters with an effective length 4.0 meters or 4.128 meters with an effective length of 3.81 meters; the uncoated thickness for both lengths is 2.67 mm; and the weight is respectively 46 kg or 44 kg. Highway guardrails have end treatments. Guardrail beams are conventionally made by roll-forming methods using steel alloy materials. The W-beam guardrail is galvanized and coated with a zinc covering to avoid corrosion and increase the life of the guardrail. AASHTO Designation M180-89 for galvanizing has a minimum single-spot test of 1,100 g/m2 (3.603 oz/ft2) and a minimum triple-spot test of 1,220 g/m2 (4.003 oz/ft2). A requirement for galvanizing is to be in accordance with ASTM A123.
A serious and very common problem with guardrails is that they are not highly visible to drivers of motor vehicles on the highways which are bordered by the guardrails due in part to the color of the guardrails, to deterioration of the guardrails and to the large number of other motor vehicles that are close to any particular motor vehicle traveling on the highway. The visibility of guardrails is very important for both daytime and night-time driving, since the guardrails should be readily apparent during the day under ambient light, and at night from the reflection of headlights and sometimes street lamps along the highway. Another problem with the visibility of guardrails is that motor vehicles travel very fast, particularly along long, slightly curved highways, requiring each driver to concentrate on the highway itself rather than on the guardrails. Furthermore, guardrails tend to be covered with dirt and dust due in part to the fast moving vehicles traveling along the highways and due in part to the weather, and there is little or no cleaning of the guardrails where they are used. Support posts are provided for supporting and maintaining the highway guardrails horizontally along the highway. The posts are anchored to the ground, and may be fabricated from metal, wood or a combination of metal and wood. One often-used requirement for metal posts is that they meet the requirements of ASTM A36/A36M.
There are various techniques which are presently being used to enhance the visibility of guardrails. These generally involve using readily visible paint or fluorescent adhesive tapes that are put on the guardrails after the guardrail system has been installed. However, it has been found in practice that these techniques do not have a sufficiently long duration of being effective, they are not as visible as would be desired, and many accidents have occurred with lateral or frontal impacts of motor vehicles. Some presently available products include an I-Beam Reflector/Protector from HSS Traffic Control Products, Fort Wayne, Ind., for attachment to guardrails, different types of reflecting devices for being attached to guardrail systems and types of reflective tapes. One reflective sheet is 3M™ Diamond Grade™ Fluorescent Sheeting, 3M Corporation, St. Paul, Minn. However, these have not proven effective. The conventional techniques of rendering guardrails more apparent to drivers are economically inefficient, particularly with installed guardrail systems, because they require an intensive maintenance program with high labor costs and the expense of replacement materials in order to keep the guardrails visible. It has recently been stated: “Chronic lack of research is highlighted with particular reference to visibility and its inadequate treatment in design standards.” Douglas Stewart, Civil Engineering 160, pp. 131-136.